This invention relates to a process and a sealing assembly in a multi-platen press for effecting and maintaining a proper sealing between two platens which produce and form a product irrespective of the distance between the two platens, or irregularities in the surface of the platen that would otherwise prevent sealing if conventional seals are employed. More particularly, a proper sealing is essential in a laminating press for efficiently heating and compressing several sheets of material in the laminating process.
The subject invention has particular application in multi-platen laminating presses for several stacks of laminates, however, it can easily be applied in any of several molding and forming machines used for a variety of material and having only one press opening.
Conventionally, sheets of material are stacked and inserted between two platens defining an opening in a multi-platen press. The distance between any two cooperating platens at any time defines an opening and a closing of the press. When this distance is at a maximum, a opening of the press occurs. At this time the stacked material is inserted in each of the openings between the platens. The minimum distance between the platens, and thus the closing of the press, is dictated by the height of the stacked material between the platens which may vary from stack to stack. A sealing element employed to allow a vacuum to be created extends within the platen opening and encapsulates the area surrounding the stacked material.
Presently, one form of this sealing element consists generally of an elastomeric lip which is associated with the bottom of a platen and moves with this platen and extends downwardly toward another platen cooperating therewith to form the opening. This general form has also been employed in a rubber compression molding press. Since this lip is of a one-piece construction and of a constant height, and the distance between the two cooperating platens vary in the multi-platen press, depending upon the height of the stacked material, a proper sealing around the stacked material is not always obtained. Due to this, the quality of the laminating process is impaired in not being able to pull the required vacuum rating and has proven to be inefficient with respect to the amount of energy in terms of heat and power applied when heating and compressing in the laminating process.